Add bd sync --check command that performs pre-sync integrity checks
without modifying state:
1. Force push detection: Detects when sync branch has diverged from
remote, indicating a potential force push
2. Prefix mismatch detection: Scans JSONL for issues that don't match
the configured prefix
3. Orphaned children detection: Finds issues with parent references
to non-existent issues
Outputs diagnostic with actionable suggestions for each problem found.
Exits with code 1 if any problems are detected.
Implements bd-hlsw.1: Pre-sync integrity check
e3b6091931